How do I write VBA script so that it will compare data? - excel

Question

We need a script to compare the dates in column D to the dates in column E.
If the date in column D is two days before the date in column E then we need column F to state that in the corresponding row to D. We have a range of 2 days before and 2 days after (shoulder days). We need to be able to easily reproduce this and have it be able to run when we import it into access. we have roughly 3300 unique days to check.
I have tried using datevalue or a formula but we need to be able to reproduce this in the future and the formula doesn't allow us to easily do that.

Answer 1

I will not provide a complete implementation, but I can show you the way how you can do it (either the Excel formula way or with VBA code). Both ways will automatically calculate the values you need so you can easily import it into Microsoft Access - the import will take the calculated values from the cells you've selected.
The first way, which is also the simplest way, is to do that with simple Excel formula, consider this picture showing how the formula will calculate the values in columns F and G:
(Note: It is showing German date format, but you can easily change that in Excel).
In column G it calculates the difference D2 - D1 and displays it in days.
Then, in column F there is a simple if condition to determine if the date D1 is less, greater or equal than D2. The Result is calculated automatically.
The formula in row 2 are:
Hint: You can drag and drop the formula to the rows 3 - n below, so you can create a lot of rows prefilled with that formula.
A second way is that you can write a VBA function for the (simple) calculation formula in column F:
Function CalcResult(D1 As Variant, D2 As Variant) As Variant
CalcResult = ""
Dim result As String
Dim diff As Single
diff = D2 - D1
If (diff > 0) Then
result = "D1 < D2"
ElseIf (diff = 0) Then
result = "D1 = D2"
ElseIf (diff < 0) Then
result = "D1 > D2"
End If
CalcResult = result
End Function
This needs to be entered in the VBA editor, which you can display if you press Alt+F11. After you have done that, press Alt+F11 again to close VBA and return to your Excel sheet.
Then, place the formula =CalcResult(E2; D2) in cell F2 as shown below:
Like in the previous example, you can drag & drop the formula to the rows 3 - n below, so you can create a lot of rows prefilled with that formula.
The advantage of the 2nd approach is that you can refine the function CalcResult later without having to change the cells again (as it is the case in the first example).
Note: The function above needs to be in a separate module and you need to save the workbook as "Macro enabled workbook" later - otherwise you'll lose the VBA code.
A third way is to use the Excel macro recorder and record whatever you intend to do. It will create a public module with VBA code. If the recorder asks you, choose to store the code in the workbook.
Later you re-visit the generated VBA code and refine it - for example, put a for loop around it to automate things you've recorded once.
This approach is good for creating a "Calculate" button and put some logic behind it.